1. Field of the Invention
The present invention relates to an apparatus for pneumatically operating the travel of a lock rod used to secure a toolholder within a toolholder receiving member. More specifically, the invention relates to utilizing a plurality of inline cylinder/piston modules to amplify the force acting upon a lock rod within the limited envelope of the spindle.
2. Description of Related Art
Clamping mechanisms for detachably connecting a toolholder to a toolholder receiving member are well known in the prior art. Such mechanisms are typically used in machining operations where the toolholder holds a cutting insert that is moved into and out of cutting engagement with a workpiece. Such an arrangement allows different toolholders holding different cutting inserts to be quickly attached to and detached from the toolholder receiving member, which in turn is connected to a device for rotating the toolholder. The present invention is intended to be utilized with a rotating toolholder and a stationary workpiece.
One commercial clamping mechanism includes a cylindrically-shaped canister member that is mateable within the tubular end of a toolholder which includes apertures for locking elements into locking engagement with recesses present in the toolholder. The locking elements, which are typically spherical, are radially moved through the apertures in a canister member by means of a reciprocating lock rod having cams that engage the locking elements. Examples of such locking mechanisms are disclosed in U.S. Pat. Nos. 4,708,040; 4,747,735; 4,836,068; and 4,932,295, each of which is assigned or co-assigned to the assignee of the present application and for which each is hereby incorporated by reference.
Looking at FIG. 1, on a toolholder 10 having a forward end 15, a cutting insert 20 is mounted. The cutting insert 20 is spaced from the toolholder 10 by a shim 25, and both the cutting insert 20 and shim 25 are held to the toolholder by means such as a clamp 30, which is secured to the toolholder 10 by a pin 35. The toolholder 10 has a rearwardly facing abutment face 40 along with a tubular shank 45 extending rearwardly from the forward end 15 and has a shank wall 50. The toolholder 10 may have a slot 53 within the shank wall 50 and spaced perforations 55 in the shank wall 50. The toolholder 10 may have forwardly facing concave contact surfaces 60 within the perforations 55. The toolholder 10 is positioned about a longitudinal axis.
A toolholder receiving member 65, having a forwardly facing abutment face 67 and an opening 70 along the longitudinal axis 56, is secured to a base member 75.
The base member 75 may be any of a large variety of anchors to which toolholders may be attached. One such example is the spindle of a rotating tool.
Within a cylindrical passageway 80 in the base member 75 is a stub 85, which also extends into the opening 70 of the toolholder receiving member 65. A bore 90 extends longitudinally through the stub 85 and a lock rod 95 is slidably mounted within the bore 90.
Toward the forward end 97 of the lock rod 95 are depressions 100 in the lock rod 95, which may be aligned with radial apertures 105 extending through the stub 85. The lock rod 95 may be moved along the longitudinal axis 56 by pulling or pushing on the lock rod base 110, which is attached to the lock rod 95. Locking elements 115 positioned within the apertures 105 of the stub 85 and within the depressions 100 of the lock rod 95 may be urged radially outwardly by moving the lock rod 95 away from the toolholder 10.
FIG. 1 shows the toolholder 10 removed from the toolholder receiving member 65. In order to secure the toolholder 10 within the toolholder receiving member 65, the lock rod 95 is positioned such that the locking elements 115 are within the depressions 100 and, furthermore, recessed within the radial apertures 105, such that the tubular shank 45 of the toolholder 10 may be inserted into the opening 70.
As shown in FIG. 2, with the toolholder 10 positioned within the opening 70, the lock rod 95 may be pulled in the direction of arrow 117 away from the toolholder 10 such that the locking elements 115 are displaced radially outwardly by cam surfaces 116 of the depressions 100 and the locking elements 115 penetrate the perforations 55, such that they contact the forwardly facing concave contact surfaces 60. When the lock rod 95 is retracted in the direction of arrow 117, the toolholder 10 is urged within the toolholder receiving member 65 and the rearwardly facing abutment face 40 of the toolholder 10 contacts the forwardly facing abutment surface 67 of the toolholder receiving member 65. This action of the lock rod 95 secures the toolholder 10 within the toolholder receiving member 65.
It should be noted in FIG. 2, that the locking elements 115 are protruding beyond the radial aperture 105 and urging the tubular shank wall 50 against the walls of the opening 70. For increased stiffness between the toolholder 10 and the toolholder receiving member 65, the lock rod 95 may be retracted further thereby causing the locking elements 115 to elastically deform a portion of the shank 45 until it contacts the walls of opening 70.
In order to provide still higher stiffness between the toolholder 10 and the toolholder receiving member 65, the tubular shank 45 may be sized relative to the opening 70 such that upon insertion of the toolholder 10 into the opening 70, there exists an interference fit and elastic deflection occurs between the shank 45 and the toolholder receiving member 65 in the vicinity of the opening 70. In such a manner the toolholder 10 may be secured to the toolholder support member 65 with a high level of accuracy and repeatability.
In order to release the toolholder 10 from the toolholder receiving member 65, the lock rod 95 is urged toward the toolholder 10 in the direction of arrow 119. In such a manner, the locking elements 115 are retracted within the radial aperture 105 and adequate clearance is provided so that the toolholder 10 may be removed from the toolholder receiving member 65.
However, given elastic deformation between the shank 45 of the toolholder 10 and the toolholder receiving member 65, there may exist high frictional forces retaining the toolholder 10 within the toolholder receiving member 65. To release the toolholder 10, the lock rod 95 is extended at the forward end of the toolholder receiving member 65 such that the lock rod 95 protrudes beyond the stub 80 and contacts an impact area 120 within the tubular shank 45 of the toolholder 10. In such a manner, continued urging of the lock rod 95 toward the toolholder 10 will force the lock rod 95 against the impact area 120 thereby ejecting the toolholder 10 from the toolholder receiving member 65.
It should now be appreciated that by urging the locking rod, a toolholder may be secured or released within a toolholder receiving member and, as such, the device shown in FIGS. 1 and 2 provides for quick changing of a toolholder.
It should further be appreciated that the forward end 15 of the toolholder 10 is not limited to the configurations shown in FIGS. 1 and 2, and may be adapted for any number of applications. For this reason, the forward end of a toolholder similar to toolholder 10 may have a large variety of configurations to provide an entire series of toolholders 10, each with a different purpose.
U.S. Pat. No. 5,870,935 is directed to a self-locking clamping apparatus for coupling a tool unit to a tool supporter, which patent is assigned to the present assignee and, furthermore, which patent is hereby incorporated by reference. The focus of this patent is to alter the angle of the ramp on the lock rod so that the ramp angle in conjunction with the locking ball in the lock rod retracted position is self-sticking. As a result of this design, the pullback force may be significantly reduced and, therefore, an object of the subject invention is to exploit this advantage with further features.
Additionally, in some instances especially for rotating applications, the envelope for the toolholder receiving member may be limited in width but may not be limited in length. Therefore, another object of the subject invention is to provide an apparatus that can provide a significant pull back and release force to the lock rod under these circumstances.